The present invention relates to a vacuum cleaner, more particularly, to a vacuum cleaner which can vary its suction force and which has a dust sensor for detecting the quantity of dust sucked.
Conventionally, a vacuum cleaner is required to perform complex functions as is required of other electritrical products. To satisfy the demand, it is proposed to provide a dust sensor to a vacuum cleaner. Specifically, a dust sensor for detecting the quantity of dust sucked is provided to a vacuum cleaner, and a detection signal from the dust sensor which corresponds to the quantity of dust sucked is displayed. When cleaning is carried out using the vacuum cleaner having the dust sensor, the degree of cleaning can be judged based upon the displayed quantity of dust sucked. Also, it is possible to judge whether or not dust to be sucked is present based upon the displayed quantity of dust sucked.
Vacuum cleaners having a dust sensor are classified into two groups. One group corresponds to vacuum cleaners which have their dust detection sensitivity set to a single predetermined sensitivity. The other group corresponds to vacuum cleaners which select dust detection sensitivities by operating a selection switch. Vacuum cleaners which belong to one of both groups are arranged to vary their suction forces.
When cleaning is carried out using a vacuum cleaner which has its dust detection sensitivity set to a single predetermined sensitivity, the cleaning usually is carried out under a strong suction force for cleaning of a carpet or the like which have long wool hair. When dust on the carpet has been completely sucked, that is when the cleaning is finished, the dust sensor may detect the pulled wool hair of the carpet. A disadvantage arises in that the vacuum cleaner cannot display the condition, in displaying the quantity of dust sucked, in which there is no sucking of dust (in other words, it displays the condition that cleaning is not finished) based upon the detection of pulled wool hair. On the contrary, when cleaning is carried out using a vacuum cleaner which has plural dust detection sensitivities and which selects one of the dust detection sensitivities by operating a selection switch, the dust detection sensitivity can be lowered by operating the selection switch for cleaning a carpet and the like under strong suction force. Pulled wool hair of the carpet is reliably prevented from being detected by the dust sensor. However, a disadvantage of this type of vacuum cleaner arises in that usage of the vacuum cleaner is complicated such that an operator must operate the selection switch so as to set a dust detection sensitivity of the dust sensor to a proper sensitivity which matches an object to be cleaned such as a wooden floor, a tatami mat, a carpet and the like. A further disadvantage arises in that no dust sucking is displayed when dust remains, or dust sucking is displayed when no dust remains, when operation of the selection switch has been forgotten for selection of the proper dust detection sensitivity. That is caused by complexity in the usage, because cleaning is carried out under an improper dust detection sensitivity for the object of cleaning.
Further, conventional dust sensors employ, as an operating voltage thereof, a voltage which is obtained by lowering the commercial power voltage to a predetermined voltage, or from a terminal voltage of a dry battery.
When the former voltage is employed as the operating voltage, disadvantages arise in that the arrangement of the vacuum cleaner becomes complicated and the vacuum cleaner becomes expensive. The reasons are that when a display device and the like for displaying a dust detection result is to be provided at a floor nozzle section for sucking dust, or at an operation section disposed at an interconnection portion of a bellows hose and an extending hose, at least two power supplying wires should be provided to the bellows hose in one body, in an entrained condition, and an electrical interconnection mechanism corresponding to the power supplying wires is needed at an interconnection portion of the bellows hose to the vacuum cleaner body. The bellows hose communicates by one of its ends to the vacuum cleaner body, and the extending hose communicates by both of its ends with the bellows hose and the floor nozzle section, respectively. A further disadvantage arises in that imperfect contact may occur in the electrical interconnection mechanism causing a claim for the imperfect contact. A still further disadvantage arises in that the dust sensor can be used in some countries but cannot be used in other countries because commercial power voltages in different countries are different from one another.
When the latter voltage is employed as the operating voltage, arrangement of the vacuum cleaner can be simplified, expense of the vacuum cleaner can be surpressed, and causes a claim for the imperfect contact are prevented from increasing, because the bellows hose is not to be provided with power supplying wires in an entrained condition. But a disadvantage arises in that the dust sensor circuitry suddenly stops its operation one day, because the dry battery has a discharging life time and the dry battery discharges gradually.